Floor Sanding And Abrasive Choice

Floor sanding is not exactly easy. Before attempting such a project consider carefully if you have the skill, patience and dedication to finish such a task once started. This article can provide some information but we generally suggest to call an expert, especially if you lack the experience.

Floor sanding can be divided into three parts. Rough, medium and fine sanding. The idea is to progressively strip the worn and damaged parts of the wooden floor, slowly smoothing the scratches left from each previous sanding round and finally achieving a flawless and pristine looking surface. The choice of sandpaper can make a huge difference in the quality of the job and must never be underestimated!

Types of Abrasives

There are several types of sandpaper but not all of them are suitable for floor sanding purposes.

Garnet. Excellent for fine sanding but wears very quickly. It is probably the best choice for hand stripping but in terms of speed of abrasion falls behind other sandpapers.

Aluminium Oxide. Can often be found in power sanders. Works not only on wood but on metal and plastic as well. It’s more durable than garnet sandpaper but isn’t as good when it comes to fine finishing. It’s relatively cheap and wears quickly on tougher wood species like oak.

Silicon Carbide. Good, all-around sandpaper with a broad range of uses from wood to metal. Its backing is waterproof and this allows you to wet sand, utilising the water as a lubricant. Abrades more than aluminium oxide but is also more expensive.

Zirconia Alumina. Comes in several variations – Zirconia, Zirconia mixed with Aluminium Oxide and Ceramic Zirconia. In terms of hardness, Zirconia is close to aluminium oxide but denser. This material is also a poor thermal conductor which minimises the risk of leaving burn marks on the surface of the floor and with less of a chance for clogging. This is the most durable and expensive type of sandpaper best used for rough sanding on uneven floors.

Most of the time, you can go with Silicon Carbide for rough sanding and Aluminium Oxide for the finer grades. Keep in mind, though, that higher quality sandpaper-like Zirconia can make it much easier for you to work and save you a lot of time. This is especially if you attempt to sand very distressed surfaces. In terms of overall effectiveness, Zirconia simply offers the most but at a higher cost.

Commercial vs Industrial Grades

There are two main types of sandpaper - commercial and industrial. If we measure the quality of the abrasive surface of sandpaper, the material used as a backing, and the glue holding those two together – industrial-grade sandpaper is always better. Unfortunately, it can only be obtained in industrial supply stores. As you can probably imagine, the commercial-grade paper is much more readily available but is of inferior quality.

Sandpaper Grits

The size of abrasive material on the sandpaper is measured in grits. There are several standards which have at least one thing in common - the lower the number of the grit, the coarser it gets. Higher grit numbers mean that the abrasive particles are getting smaller. High grit sandpaper will strip less wood but with less scratching and leaves a smoother surface.

One of the most important parts of the wood floor restoration process is the choice of abrasive. Using the right abrasive would ensure easy floor sanding, minimum wood waste and smooth floor surface after the floor sanding is completed.

There are many abrasive grits in wood finishing. The most frequently used grits in the floor restoration are:

• 24 grit
• 40 grit
• 60 grit
• 80 / 100 grit

You should take into consideration the condition of your wooden floor while choosing the grit of the floor sanding paper to start with. For wooden floors in poor condition with many scratches, bad level, uneven surface, which have not been sanded before, the coarsest grit abrasive is the most appropriate to start with. That would be 24 grit sanding paper.

For wooden floors in a good condition, which have been sanded before, 40 grit or 60 grit sanding paper might prove a better choice.

Most timber species used for flooring can be finished in 80 or 100 grit and screen buffing will follow of grits 120, 150 or 180 - depending on the softness of the timber.

When you sand, you first use coarser grits for rough sanding and progressively move to higher ones. A coarse grit will be very aggressive but will also leave scratches. Those flaws will be eliminated by the higher grit sandpapers which in turn will also leave marks until this is no longer a problem. It is entirely possible to simply use the highest grid sandpaper available but this will both costly, ineffective and time-consuming. Skipping grits is a very bad idea because it will leave dents and scratches. The transition must be smooth or your floor won’t be.

Even if your floor is in bad condition that doesn’t immediately mean you have to use the coarsest grit available. It depends on the type of wood (there is a huge difference between pine and oak), the type of floor (parquet and engineered require more attention than solid wood) and the machine you are going to use. A belt sander, for example, will offer much more control than a drum sander.

Refinishing Advice:

• Make sure your coarsest grit can level the floors as well. Repeat as much as necessary.
• Make sure your next grit can remove the marks from the previous one.
• For a perfect job use the finest grit of sanding paper.
• Change abrasive frequently, whenever necessary.
• Make sure your sanding belt is calibrated.